The present invention relates to an electrical heater having a heating element combined with a temperature-sensitive device for controlling the operating temperature of the element as a function of ambient temperature.
U.S. Pat. No. 4,072,847 discloses such a heater which comprises a glass tube within which is sealed a tubular enclosure comprising a first tube closed at one end and a second tube joined in water-tight fashion to the other end of the first tube. A heating element is within the first tube and a thermostat for the heating element is within the second tube. The first tube is of metal and the second of translucent or transparent plastic, and, in order to meet British Standards No. 3456, the heating element is separated from the metal tube by a tube of insulating material. However, it has now been realized that the tube of insulating material and the air trapped between it and the metal tube considerably reduces the heat transfer from the heating element. It is an object of the invention to improve the heat transfer.